| With the rapid development of global green energy,capturing energy from environmental vibrations and powering MEMS has become the focus of research and development in academia and industry.Piezoelectric energy harvesters(PEHs)have the advantages of low processing difficulty,good energy capture effect and wide application range,so they are favored by researchers.The cantilever beam PEHs can only generate a considerable response voltage when the environmental excitation frequency is close to their natural frequency.However,the excitation frequency in the environment is generally low,and the natural frequency of traditional piezoelectric beams is much greater than the excitation frequency in the environment,which makes it difficult to meet the resonance conditions.In order to solve the above problems,this paper takes two kinds of piezoelectric beams with periodic structure as the research object,and uses finite element software to analyze their low-frequency and broadband performance,mechanical performance and energy capture performance,and explore the influencing factors of its energy capture performance,which has reference value for the design of ultra-low frequency,broadband,high-performance PEHs.The main research work of this paper is as follows:(1)The electromechanical modeling of the single crystal piezoelectric beam is carried out,the expression of its output voltage is derived,and the factors that affect the output voltage of the piezoelectric beam are clarified.Substituting the parameters of the piezoelectric beam into the expression,the calculation results show the necessity of the excitation frequency near the natural frequency of the piezoelectric beam,which provides a theoretical basis for the subsequent research.(2)Finite element software is used to solve the low-order natural frequencies of piezoelectric beams with periodic structures,folded beams and spiral beams.The effect of the number of segments on the natural frequency is discussed.The results show that increasing the number of segments can reduce the natural frequencies of the two beams,shorten the adjacent natural frequencies of the two beams,and effectively improve their environmental vibration energy capture performance.When the number of segments is greater than 8,the low-frequency performance of the folded beam is relatively good,but the broadband performance of the spiral beam is better than that of the folded beam.(3)The strength,mode shapes,stress and response voltage of two kinds of piezoelectric beams with periodic structure and traditional piezoelectric beams are compared and analyzed.The results show that although traditional beams are stronger than periodic structure beams,their low-frequency and broadband performance are far inferior to periodic structure beams,and their response voltage is also lower than that of periodic structure beams.At the same time,the influence of the number of segments on various properties is discussed.The results show that increasing the number of segments will increase the stress on the periodic structure beam.Changing the number of segments will not change the beam’s mode shape,and the modal stress is always at the corners of the two segments.The response voltage of the spiral beam changes with the number of segments has a certain periodicity,and the response voltage of the folded beam changes with the number of segments monotonically.(4)The influences of thickness of piezoelectric plate and substrate,beam length,mass block size,mass block position,clamping position,piezoelectric plate arrangement and distance between center axis of beam on the energy capture performance of spiral beam and folded beam are discussed,the orthogonal experimental method is used to optimize the structure of the two beams.The results show that after optimization,the first-order natural frequencies of the spiral beam and the folded beam are reduced by 15.59% and 27.34%,and the first-order response voltage is increased by 200.79% and 173.33%,respectively. |
PDF Full Text Request